Said compositions were known from e.g. U.S. Pat. No. 4,314,918, WO 96/20968, WO 96/23034.
From U.S. Pat. No. 4,314,918, coating compositions were known, the vehicle portion of which essentially consisted on a weight solids basis, of:
(a) from 35 to 55 wt % of a cross-linking agent, selected from a vast variety of all possible cross-linking agents; PA1 (b) from 15% to 50% of a curable polyol resin; and PA1 (c) from 15% to 50% of a reactive diluent derived from the reaction of (i) from 0.25 to 4 moles of a glycidyl ester with (ii) each mole of a functional material having a molecular weight of less than 1000, a hydroxy equivalent weight of from 30 to 1000 and a carboxy equivalent weight of from 50 to 1000, provided the total hydroxyl and carboxyl functionality of the functional material is at least 2.0. PA1 (a) 5 to 50 percent, by weight of total binder, of one or more hydroxy-functional oligoesters, having at least one hydroxyl group on each of at least three separate branches of the oligoester, a polydispersity of less than 2.5, a hydroxyl value of between 80 and 280, and a number average molecular weight (Mn) between 150 and 3000, PA1 (b) 10 to 90 percent by weight of the total binder, of a hydroxy-functional acrylic or methacrylic copolymer with an Mn between 500 and 15000, having a hydroxy-functional comonomer content between 10 and 50 weight percent of the copolymer and at least 10 percent of comonomers selected from the group consisting of alkyl-substituted cycloaliphatic meth(acrylic) comonomer and/or alkyl-substituted aromatic vinyl comonomers and combinations thereof, wherein the alkyl-substituted cycloaliphatic group on said comonomers had at least nine carbon atoms and the alkyl-substituted aromatic group on said comonomers had at least ten carbon atoms. PA1 (a) 5 to 50 percent by weight, relative to the weight of the binders, of one or more hydroxy-functional oligoethers derived from at least one polyol, free of carboxyl groups and having three or four hydroxyl groups, and a mono-glycidyl ester of a branched carboxylic acid, containing from 5 to 13 carbon atoms, the oligoether having a number average molecular weight (Mn) of from 150 to 1000 g/mol, a molecular weight distribution (MWD) &lt;1.10 and a hydroxy value of between 180 and 700, PA1 (b) 40 to 60 percent by weight, relative to the weight of the binder, of one or more hydroxy-functional acrylic or methacrylic copolymer with a Mn between 500 and 2500, having a hydroxy-functional comonomer content between 10 and 50 weight percent of the copolymer derived from the reaction products of mono-glycidyl esters of a branched carboxylic acid containing from 5 to 13 carbon atoms and acrylic acid or methacrylic acid, and combinations thereof, and optionally mixed with an amount of at most 10% by weight relative to the total weight of comonomers, selected from the group consisting of cycloaliphatic (meth)acrylic comonomers and/or alkyl substituted aromatic vinyl monomers, PA1 wherein the alkyl-substituted cycloaliphatic group on said comonomers has at least nine carbon atoms and the alkyl-substituted aromatic group on said comonomers has at least ten carbon atoms, PA1 (c) 5 to 40 percent, relative to the weight of the binder, of polyisocyanate cross-linkers, PA1 (d) an effective amount of curing catalyst. PA1 (a) 10-50 weight percent, preferably 20-50 percent, by weight of the copolymer, of a hydroxy-functional monomer; and PA1 (b) 0-10 weight percent, of comonomers selected from the group consisting of alkyl-substituted cycloaliphatic (meth)acrylic comonomers, alkyl-substituted aromatic vinyl comonomer and combinations thereof, wherein the alkyl-substituted cycloaliphatic group is at least C.sub.9 (has at least nine carbon atoms, preferably 9 to 12) and the alkyl-substituted aromatic vinyl group is at least C.sub.10 (has at least 10 carbon atoms, preferably 10 to 12); PA1 (c) 0-80 weight percent, preferably 25 to 50 percent, of other copolymerizable comonomers.
The reactive diluent was characterized by an acid number of less than 50, a non-volatile content of greater than 85% and a Gardner-Holdt viscosity of less than Z-10.
However, by application of the disclosed preparation processes, high solid content reactive diluents of 95% or more, as presently required by modern paint industry economics and by environmental and health authorities, could not be obtained, and the coating compositions obtained according to the examples VII and VIII actually showed relatively low solids contents and the drying/curing of these coatings could not be attained at ambient temperatures, so that a baking step after application was necessary.
Moreover, it will be appreciated that the coating composition according to example VIII comprised a binder without acrylate copolymers. Such binder forms very dense cross-linked cured coating films, which showed totally unattractive film properties, i.e. too hard and too glassy films. The coating obtained with the product obtained according to example I, and the usable polyisocyanates appeared to form an inferior coating film only and showed moreover an unacceptable drying/curing.
WO 96/20968 disclosed coating compositions, comprising as separate binder components
As preferred hydroxy-functional oligomer were used oligoesters obtained by the reaction of a branched polycarboxylic acid and a monoepoxyester. Actually applied hydroxy-functional oligomers, providing acceptable final coating compositions, were the product of a ring opening polycondensation reaction in which a multifunctional polyol is reacted with an acid anhydride and subsequently with an epoxide.
On the other hand polymeric vehicles for high solids coatings were known from WO 96/23034, which comprised a blend of at least one non-mesogenic substantially linear oligoester diol and at least one hardener which was a mesogenic polyol, phenolic ester alcohol or crystalline polyol, which blend is effective for reaction with a cross-linker, which is reactive with the non-mesogenic oligoester and hardener.
The mesogenic polyol had a number average molecular weight in the range of from 186 to 4000, a polydispersity index of not more than 2.6 and comprising from 5 to 50 weight percent mesogens, the crystalline polyol was oligomeric or non-oligomeric and had from 5 to 200 carbon atoms, the oligomeric crystalline polyol had a number average molecular weight in the range of from 400 to 4000, the non-oligomeric polyol had a molecular weight in the range of from 120 to 500, and a solubility in the formulated coating composition of not more than 10 g/l at a temperature of from 0.degree. C. to 40.degree. C.
The phenolic ester alcohol having at least two ester groups; at least one aliphatic hydroxy group and at least one phenolic hydroxy group.
Preferably the mesogenic polyol had the general formula EQU R-T-E-F-R,
wherein R is the adduct of a mono-oxirane, which contained not more than 25 carbon atoms.
From WO 97/13741 low viscosity, high solids polyesterdiols and coating compositions containing them, were known.
Said polyesterdiols had low viscosities of less than 3500 cps, high content of non-volatile matter in excess of 96 wt %, and narrow molecular weight distribution of less than about 1.4. They were prepared by esterification of one or more aliphatic dicarboxylic acids or ester derivatives thereof, using at least a 1.5 molar excess of one or more aliphatic diols until an acid number of less than 20 is achieved, and stripping excess diol from the polyesterdiol reaction product. Where esterification catalyst was used, the catalyst is substantially removed prior to stripping excess unreacted diol from polyesterdiol reaction product.
The polyesterdiols so produced had been found to be useful in particular as coatings, paints and adhesives, providing coatings with reduced content of volatile organic compounds but combined with an unpracticable viscosity under normal operation conditions.
Because of an increasing pressure from health authorities and/or environmental authorities, the emissions of volatile organic compounds (VOC) and mainly of organic solvents during baking of the original resin composition, must be reduced by paint and coating industry and further extensive research efforts have been directed on the aim to provide low VOC coating compositions, which moreover, show a sufficiently low viscosity in order to meet modern coating application requirements, and acceptable final properties of the coating composition after baking.
Due to economic pressure from paint manufacturers and their customers, there is a strong need for lower drying temperatures and shorter application times in combination with an improved pot life.
It will be appreciated that as predominant trend has been derived by persons skilled in the art from the hereinbefore discussed prior art the use of least of low molecular weight oligoesters as binder component.
However, increasing the solids content of paints by adding reactive diluents can deterionate either pot life, or drying and curing behaviour of the applied paint.
Therefore an object of the present invention is to provide improved coating compositions, showing an attractive combination of viscosity, VOC and final physical properties, such as hardness, flexibility, and pot life and drying behaviour.
Another object of the present invention is to provide new binder components to enable the hereinbefore specified coating compositions.
As a result of extensive research and experimentation such as coating compositions aimed at and binder components to be used therein have surprisingly been found now.